DIAGNOSTIC (VIRAL) TESTS
Shows current infection |
ANTIBODY TEST
Shows past infection |
||
Also known as |
Molecular Test
|
Antigen Test
|
Antibody Test
|
---|---|---|---|
When the test is recommended |
|
|
|
How the test works |
Detects genetic material (RNA) within the COVID-19 virus |
Detects proteins (or antigens) on the surface of the COVID-19 virus |
Detects antibodies made by the immune system in response to COVID-19 infection |
How the test is done |
Saliva, or swab from nose or throat |
Swab from nose or throat |
Blood from arm or finger stick |
How long it takes to get results |
Typically, 2-6 days but some locations offer same day or even one- hour results |
Most are rapid, approximately 15 minutes or less. |
Same day to 3 days |
What the test does |
Checks for active coronavirus infection |
Checks for active coronavirus infection |
Checks for past coronavirus infection |
What a positive result means* |
A positive result means you have COVID-19. The test detected the COVID-19 virus.
NOTE: If you had COVID-19 within the past 90 days and you now have a positive test but no symptoms, talk with your doctor to see if you have COVID-19 again. |
A positive result means you have COVID-19. The test detected the COVID-19 virus.
|
A positive result means that you have been infected by COVID-19 in the past. The test detected antibodies to the COVID-19 virus. |
What a negative result means* |
A negative result means the test did not detect the virus at the time the test was taken. A negative result can also happen if the test was taken too early or the test missed your infection. Note: If you are a close contact to a person with COVID-19 you must remain under quarantine for the entire time because you may still be infected but it was too early for your test to be positive. |
A negative result means the test did not detect the virus at the time the test was taken.
Note: If you are a close contact to a person with COVID-19 you must remain under quarantine for the entire time because you may still be infected but it was too early for your test to be positive. |
A negative result means the test did not detect antibodies to the COVID-19 virus and you may have never had COVID-19 (see antibody section below). |
*No test for COVID-19 is perfect. Any test may produce:
A downloadable infographic summary is available: Types of Coronavirus Tests
Testing is highly recommended for:
In addition, people without symptoms who believe they may be currently infected should consider getting tested.
Testing is not recommended for people who had a positive viral COVID-19 test in the last 90 days and do not currently have symptoms of COVID-19.
After the test, make sure that you understand what your result means and what to do next.
Your COVID-19 Test was POSITIVE
A positive result means you have COVID-19. The test detected the COVID-19 virus.
You must isolate yourself:
Even if you had no symptoms, you are still infected and you can still pass the virus onto other people. If you start feeling sick, you must stay home longer, see If you’ve been sick above.
Tell all of your close contacts to quarantine: give them the quarantine instructions available at ph.lacounty.gov/covidquarantine.
Follow the full isolation instructions: ph.lacounty.gov/covidisolation.
Answer the call from LA Public Health: Help slow the spread of COVID-19 by answering if you get a call from “LA Public Health” or (833) 641-0305. You can also call (833) 540-0473.
Your COVID-19 Test was NEGATIVE
A negative COVID-19 result means the test did NOT detect the COVID-19 virus at the time you took the test. But it is possible that the test is wrong and that you are infected. This can happen if the test is taken too early or if the test misses your infection. Even if the result is correct, because there is so much COVID-19 around, you could become infected at any time. Practice everyday prevention including physical distancing, wearing a mask over your nose and mouth, and avoiding crowded places (especially indoors).
This is because antigen tests often miss infections. See Information for Patients with Symptoms Who Have a Negative Antigen Test.
If you are not sure what kind test you got, look at your test result report, ask your provider, or look on the webpage where you booked the appointment.
You may still be infected, but it is too early to show on the test.
You need to stay in quarantine for 10 days after you last had close contact with the person with COVID-19.
Follow the full quarantine instructions at ph.lacounty.gov/covidquarantine.
You were probably not infected with COVID-19 on the day your test was taken.
Antibody tests (also known as serology tests) are blood tests that look for antibodies against a virus. They do not look for the virus itself. Antibodies are proteins that are made by the immune system to help fight infection. It takes about one to three weeks after the start of COVID-19 symptoms for the body to make enough antibodies to be found by a test. Some people may take even longer and some people who were infected with COVID-19 may never develop antibodies.
We do not know yet if having antibodies to the virus can protect someone from getting infected again, and if it does, how long that protection (immunity) might last. Until more is known, even if you had a positive antibody test, you should continue to practice everyday prevention to protect yourself and others, including keeping your physical distance from others, correctly wearing a mask, and washing your hands often. Continue to choose wisely and avoid the 3 C’s (confined spaces, crowding, and close contact).
Antibody test results should not be used to determine if someone can return to work or to decide who can spend time together.
To learn more about using antibody tests to look for past infection, visit the CDC webpage.
Uses of antibody tests
To guide the management of someone with complicated symptoms
There are situations where a serology test may be helpful (in addition to a viral test) to diagnose COVID-19, such as:
For science and public health
Scientists and Public Health organizations are using antibody tests to learn more about how the immune system responds to the COVID-19 virus over time. Antibody tests can tell how many people in a community may have been infected in the past and how far the pandemic has progressed. They can also be used to help understand why some people get infected but never show any symptoms (asymptomatic infection).